Production of unsaturated nitriles by selective oxidation



United States Patent 2,701,260 PRODUCTION OF UNSATURATED NITRILES BY SELECTIVE OXIDATION Hugh J. Hagemeyer, Jr., Kingspoi't, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application October 19, 1950, Serial No. 191,072

4 Claims. (Cl. 260465.9)

This invention relates to a process for the production of unsaturated nitriles. More particularly, this invention concerns a process of producing unsaturated nitriles, exemplified by acrylonitrile and methacrylonitrile, by the selective oxidation of the corresponding saturated nitriles, such as propionitrile and isobutyronitrile.

It is known in the art to produce saturated nitriles by various methods such as by the reaction of an aliphatic acid with ammonia. It has also been proposed in the art to convert saturated nitriles to unsaturated nitriles by dehydrogenation over a dehydrogenation catalyst. That is, the saturated nitrile is passed in contact with dehydrogenation catalysts exemplified by oxides of platinum and palladium carried on suitable supports and at an elevated temperature. However, certain of such prior art processes involving dehydrogenation have not been too satisfactory for various reasons. For example, the yields may be rather low in such processes. Also there is a tendency for the dehydrogenation catalysts to become deactivated by the deposition of carbon thereon.

Inasmuch as there is considerable commercial demand and use of unsaturated nitriles, exemplified by acrylonitrile and the like, it is apparent that the provision of an improved process whereby saturated nitriles may be more readily and efiiciently converted to unsaturated nitriles is a highly desirable result.

After extensive investigation, I have found a new method utilizing selective oxidation whereby saturated nitriles may be quickly and efficiently converted to unsaturated nitriles as will be set forth in detail hereinafter.

This invention has for one object to provide a new method of converting saturated nitriles to unsaturated nitriles. Another object is to provide a method for converting saturated nitriles to unsaturated nitriles by selective oxidation. A still further object is to provide methods of the class just described wherein a screen or gauze type of catalyst may be effectively employed. A particular object of this invention is to provide a method of selective oxidation whereby propionitrile may be converted to acrylonitrile. Another similar object is to provide a method of selective oxidation whereby isobutyronitrile may be converted to methacrylonitrile. Other objects will appear hereinafter.

In the present invention I have found that the lower aliphatic saturated nitriles can be selectively oxidized in good conversions and yields and without deactivating the catalyst by employing an exothermic reaction w th oxygen and/or air and oxygen containing gases using metal catalysts such as silver, copper, gold, platinum, palladium, ruthenium and iridium and alloys thereof.

Patented Feb. 1, 1955 amounts of suitable promoters such as the oxides of alkaline earth metals, and the oxides of tin, antimony, bismuth, titanium, zinc and zirconium.

The reaction is represented by the following equations showing the selective oxidation of propionitrile and isobutyronitrile to acrylonitrile and methacrylonitrile respectively.

(II) 2(CHa)zCHCN+Oz 2CH2=C(CH;)CN-|-Hz0 Some acrylonitrile is also formed in the production of methacrylonitrile by straight thermal cracking. (CHa)zCHCN m CH2=CHCN+ CH4 A further understanding of my invention will be had from the general description which immediately follows and a consideration of the several specific examples set forth hereinafter.

The saturated nitrile to be reacted is vaporized and preheated to ISO-600 C. Air and/ or oxygen or oxygen containing gases are mixed with the preheated nitrile feed immediately before or in the catalyst bed and reacted to form the unsaturated nitrile. The reaction is usually carried out at temperatures in the range S00800 C. and using contact times of 0.001 to 2.0 seconds. The molar ratio of oxygen to nitrile can be varied within wide limits depending on the preheat temperature, contact time and reactor temperature used and the conversion per pass desired. The reactor temperature can be controlled by regulating the molar ratio of oxygen to nitrile. l have also found it advantageous to use molar quantities of oxygen less than that required to maintain the desired reactor temperature and to apply some external heat.

Although silver, copper, gold, platinum, palladium, ruthenium and iridium and mixtures and alloys thereof can be used in a variety of shapes and forms it is generally preferred to use a close pressed bundle of fiat screens. This insures an even distribution of heat throughout the reactor space and helps to avoid local hot spots, catalyst fusion and excessive burning of the nitrile feed. Normal, increased, or decreased pressures may be used.

The invention is illustrated in the following examples:

EXAMPLE 1 The reactor used in this set of runs was a double walled vessel 21 inches long by 1.25 inches 0. D. with 0.16 inch clearance between the inner and outer walls. It was piped up so that propionitrile vapors entering at the bottom from the vaporizer passed upward through the outer tube, mixed with air, with or without diluents at the top and then passed downward through the inner tube which contained the catalyst. The nitrile vapors were preheated by exchange in the upward passage through the reactor. Immediately after leaving the reactor the gas stream was rapidly cooled by glycol condensers. Catalysts used, average temperatures in the reaction zone, ratio of propionitrile to gram atoms of oxygen, contact times, conversions, and ultimate yields are reported in the Table I.

Table I Run No.

Average Temp. Reactor Zone, C.

G. M. EtCN/ G. Atom Oxygen Ultimate Yield Catalyst Copper pellets, 631 g Copper pellets, 130 g. Silver Wire, 332 g... Silver Wire, 212 g Copper pellets *Isobutyronitrile oxidized to methacrylonitrile (MAN).

The metals are conveniently used in the form of pellets, wire screen, gauze, and/or perforated metal plates. Silver and copper are the preferred catalysts because of cost and in general copper is used where an easily poly- EXAMPLE 2 In this series of runs propionitrile was vaporized and passed through a preheater with or without a diluent.

merizable unsaturated nitrile is formed. The particular and/01 Oxygen Containing gases y P1115 metal catalyst can be painted or coated with small were mixed with the nitrile feed in or immediately before reaching the catalyst space. The reaction is exothermic and the temperature in the reactor space was controlled by the throughput, the preheat temperature, and the gram mole ratio of propionitrile to gram atoms of in the art. Hence, I do not wish to be restricted in my invention excepting insofar as it is necessitated by the PI'IIOI 1ar t and the spirit of the appended claims.

c aim:

oxygen. The preheater was a vertical tube one inch 0. D. 5 1. A process of converting a saturated lower aliphatic by 24 inches long and was topped by a reactor space 1.5 nitrile to an unsaturated nitrile having the same number inches 0. D. and 6 inches long. The preheater tube is of carbon atoms which comprises preheating said satupreferably packed with an inert material and catalysts rated nitrile, contacting said saturated nitrile with a noble used included silver, copper, platinum, palladium and metal catalyst comprised of a metal from the group conrhodium and mixtures thereof. Catalysts, average reac- 10 sisting of silver, copper, gold, platinum, palladium, tion temperatures, nitrile to oxygen ratios, contact times, ruthenium and iridium and at a reaction temperature conversions and ultimate yields are reported in Table II. between 300-800 C., said contacting with the catalyst Table III reports results for the manufacture of methtaking place in the presence of oxygen as a primary reacrylonitrile from isobutyronitrile with byproduct acryloactant whereby a substantial portion of the saturated nitrile by this method. nitrile is oxidized to an unsaturated nitrile.

Table II TAve.

emp. as. catalyst EtCN/0 as. ere

7% Pt,93% Ag wires 620 280 3.44 0. 49 8.21 77.1 Pt, 80% Ag 100 mesh 070 270 1.75 0.11 14.7 62.3 Pl a t iifii r ri Screens, 100 mesh- 460 270 2. 9s 0. 5.23 79.8 Ag screens 100 mesh 690 290 2.01 0.060 11.4 67.0 Cu Screens, 50 mesh 670 295 4. 50 0.034 12.1 70.0 ..do e90 340 4. 50 0.003 13.7 81.0 50% Cu, 50% Ag Screens 690 335 4. 50 0.061 9.2 72.0

Table III Tem Tem Conv.to Percent Run No. Catalyst 0 o a o IBN/O 3 Reactor Preheat AN MAN Yield Copptg Screen 100 640 300 3.2 0. 3.1 23.7 as "Fifi; 010 280 3.0 0.07 2.2 14.1 71 Copper Pellets 630 310 2.5 0.18 2.7 18.6 82 Ag Screen, 100 mesh. 640 290 3.0 0. 20 1.9 21.4 86

In the above tables summarizing a substantial num- 2. A process for converting a saturated lower aliphatic ber of runs which were conducted with the various catanitrile having from 3 to 5 carbon atoms to an unsaturated lysts and on different saturated nitriles with different nitrile having the same number of carbon atoms, said contact times, etc., the symbol EtCN refers to the satuprocess comprising contacting a gaseous mixture of the rated nitrile propionitrile. The abbreviation IBN refers saturated nitrile and oxygen with a noble metal catalyst to the saturated nitrile isobutyronitrile. Since these selected from the group consisting of silver, copper, gold, saturated nitriles are known chemical compounds, explatinum, palladium, ruthenium, and iridium at a reactensive discussion of methods of preparation are unnecestion temperature in the range of 300-800 C., and with a sary. The saturated nitrile used in our process may be contact time of only a fraction of a minute, the composiobtained from any suitable source. However, in the tion of the gaseous mixture of the saturated nitrile and way of example, it is mentioned that EtCN may be preoxygen being within the range of 1.22 gram mols of pared by the reaction of propionic acid and ammonia in nitrile per gram atom of oxygen to 4.50 gram mols of the presence of a suitable catalyst such as phosphoric acid nitrile per gram atom of oxygen. impregnated aluminum oxide at a temperature between 3. A process which comprises contacting a saturated 400550 C. The propionic acid and ammonia are aliphatic nitrile having from 3 to 5 carbon atoms together passed over the catalyst to give propionitrile with a substantial portion of oxygen with a metallic silver (CHBCH CN) screen catalyst mamtarned at a temperature between 2 300 c. and 800 0., whereby the saturated nitrile is plus water. Likewise, the IBN may be secured from oxidized to the corresponding unsaturated nitrile. any suitable source as, for example, manufactured by 4. The process which comprises contacting propionithe reaction of isobutyraldehyde and ammonia in the trile and oxygen as primary reactants with a copper presence of a suitable catalyst such as a supported screen catalyst at a temperature between 300800 C. chromium oxide catalyst. The abbreviations AN and whereby acrylonitrile is formed. MAN in the above tables refer to acrylonitrile and methacrylonitrile, References Cited in the file of this patent It is believed that it may be seen from the foregoing that I have provided a relatively direct and efiicient UNITED STATES PATENTS method for converting saturated nitriles to unsaturated 2,384,737 Haas Sept. 11, 1945 nitriles. As may be observed from the data set forth 2,385,552 Spence et al Sept. 25, 1945 above respecting the several examples operated at dif- 2,412,437 Wagner Dec. 10, 1946 ferent temperatures and at different contact times, etc., 2,445,693 Porter et al July 20, 1948 that relatively high yields of the order of greater than 2,452,505 Teter Oct. 26, 1948 may be secured. It will be observed that the con- 2,481,826 Cosby Sept. 13, 1949 tact time of the saturated nitrile and oxygen with the 2,499,055 Cosby et al. Feb. 28, 1950 catalyst screen is preferably quite short liilild preferably 2,554,484 Loder May 29, 1951 only comprises a fraction 0 a minute. at is, contact times which do not exceed /2 minute are preferred. 80 FOREIGN PATENTS While in Example 1 I have referred to certain reactor 790,262 France Nov. 16, 1935 construction, this is primarily for the purposes of illus- OTHER REFERENCES tration and my novel process may be carried out in ano other suitable catalytic reactor. Certain other changes Berkman et al.: Catalysis (Reinhold), pp. 892, 904

in the present invention will be apparent to those skilled 

1. A PROCESS OF CONVERTING A SATURATED LOWER ALIPHATIC NITRILE TO AN UNSATURATED NITRIL HAVING THE SAME NUMBER OF CARBON ATOMS WHICH COMPRISES PREHEATING SAID STAURATED NITRILE, CONTACTING SAID SATURATED NITRILE WITH A NOBEL METAL CATALYST COMPRISED OF A METAL FROM THE GROUP CONSISTING OF SILVER, COPPER, GOLD, PLATINUM, PALLADIUM, RUTHENIUM AND IRIDIUM AND AT A REACTION TEMPERATURE BETWEEN 300-800*C., SAID CONTACTING WITH THE CATALYST TALKING PLACE IN THE PRESENCE OF OXYGEN AS A PRIMARY REACTANT WHEREBY A SUBSTANTIAL PORTION OF THE SATURATED NITRILE IS OXIDIZED TO AN UNSATURATED NITRILE. 